Biopsy specimens can be obtained by surgical excision or needle biopsy procedures. In general, a needle biopsy procedure involves inserting a cannula-and-stylet assembly through an incision until the tip of the assembly is at or near the site from which a biopsy specimen is desired. After positioning of the assembly, the stylet is withdrawn and the cannula is inserted further to collect a specimen in its distal end. Suction is then applied to the proximal end of the cannula, usually by means of a conventional syringe, to obtain or assist in severing the specimen for subsequent histologic and/or cytologic examination in a laboratory.
Such biopsy specimens can be utilized to diagnose a wide variety of diseases. For example, there are over one hundred forms of cancer, which is the second leading cause of death in the United States, and fluid, tissue and bone marrow biopsies are widely utilized to diagnose and treat some forms of cancer. It will thus be appreciated that the quick retrieval of such specimens with minimal discomfort and trauma to the patient is important to the success of such procedures.
A variety of biopsy needle units have been available heretofore. In general, such units include an outer cannula or hollow needle with a removable inner needle and/or solid stylet extending therethrough. Some releasable locking means is generally provided for securing the inner needle and/or the stylet in longitudinal position within the outer needle. For example, U.S. Pat. Nos. 4,356,828; 4,266,555; 4,262,676; 3,628,524; and 3,598,108 to Jamshidi are representative of the prior art in this area. Such devices, however, require re-sterilization after each use and also require re-sharpening after a few uses, and thus tend to be relatively expensive.
As a result, various attempts have been made to develop biopsy needle units which are partially or completely disposable. For example, my prior U.S. Pat. No. 4,314,565 shows a biopsy needle unit wherein the needle is removably secured by a threaded collar in the chuck of a generally T-shaped stainless steel handle. This unit utilizes a replaceable needle, which can be sterilized and sharpened for reuse, or disposed of after each use, but the handle still requires sterilization after each use.
Completely disposable biopsy needle units have been available heretofore, however, these have not been altogether satisfactory either. Such units tend to incorporate stainless steel needles with plastic handles which in turn is a critical stress junction. Breakage or slippage at this junction during insertion of the needle can cause injury to the patient. Similarly, breakage or slippage at the junction between the solid stylet and its end cap can cause injury to the doctor performing the precedure. It will be appreciated that considerable pushing and twisting forces are applied to such devices during use, particularly while obtaining bone marrow specimens.
Some of the disposable biopsy needle units of the prior art have been of three-piece construction with a separate cover cap for securing the stylet in place, which cap can be difficult to remove particularly with gloved hands. For example, disposable bone marrow biopsy/aspiration needles of this type are available from Monoject division of Sherwood Medical of St. Louis, Missouri. U.S. Pat. No. 4,258,722, to Sessions is also representative of the prior art in this regard.
Other biopsy needle units of the prior art have been of two-piece construction, but with other drawbacks. For example, U.S. Pat. No. 4,469,109 to Mehl shows such a two-piece unit; however, the stylet is secured to the needle by means of a button-and-spring detent locking-groove that requires a twisting motion to engage or disengage, which can be inconvenient if not awkward with gloved hands. A converging bore is provided for receiving the end of a syringe for aspiration, but no means are provided for quickly and conveniently securing the syringe and needle together. As a result, the doctor usually requires an assistant to complete the procedure.
A need has thus arisen for an improved disposable biopsy needle unit of inexpensive but safe, secure, and reliable construction which is also comfortable and easy to manipulate by one person.